Seems like most people think of cycling as a seasonal activity. I've been commuting by bike day in and out for a couple years now, in all kinds of weather, but there are a couple of days each year that mark the cycling seasons. One is the first day of spring, when it seems like everybody gets out on a bicycle to enjoy the nice weather. Another is a day like today, when you realize that you have to prepare for the serious cold weather. Today the temperature started around 17°F and made it all the way up to 25°F. It'll be like this all week. But on the first day, I head out a little prepared for ordinary cold jst above freezing, and once again learn an important lesson. In winter, I'm willing to cycle around town down into the single digits, almost 30°F below freezing, but dressing for that kind of weather takes a little adjustment.
My normal winter gear is a fleece jacket under a winter coat shell, a knit cap that covers my ears, a wool scarf and some gloves. For the serious cold weather, you need windproof gloves, like ski gloves, a couple more shirt or sweater layers, and maybe thermal underwear or wool socks. Cycling in the cold is not really all that bad, as long as you have windproof clothes over layers, because you generate heat as you work. Windproofness is important, though, because there's an inherent wind chill when you're cycling along at ten or fifteen miles an hour. And at least if it's 15°F below freezing, there's little chance of rain and rarely high winds, which are the real irritating weather for cycling.
For some perspective though, I looked up today's weather for Louisville's sister city Perm, in the middle of Russia. Today's weather was not all that different; it was 15°F-24°F in Perm. But Tuesday night, it's supposed to get down to -22°F.